Feasibility of Using Photophoresis to Create a Concentration Gradient of Solvated Molecules
B. Space, H. Rabitz, A. Lõrincz and P. Moore
Journal of Chemical Physics
105,
9515--9524
(1996)
Abstract
The objective of this work is to estimate the feasibility of creating
a measurable concentration gradient of molecules in a solvent by a
laser driven photophoresis process. The molecules are dissolved in a
suitable solvent that is not significantly absorbing at the applied
radiation frequency. The molecule is anisotropic, or ideally
propeller shaped, and has an appropriate transition dipole capable of
driving ro-vibrational motion. The polarization of the laser can be
taken as rotating slowly with the molecules. The resulting torque
driven hindered rotation imparts a forward thrust, and thus
creates a net flow of the molecules which can set up a concentration
gradient in a finite cell. The relevant physical parameters are
estimated with the aid of molecular dynamics simulation methods on a
prototype system, and the results indicate that a detectable
concentration gradient may be established. A practical issue is to
treat heating and resultant mixing or turbulence in the medium.
Laboratory experiments are needed to further explore the photophoresis
process.
